Atherosclerosis is one of the common diseases associated with exposure to environmental and industrial pollutants. Until fairly recently, pro-inflammatory interactions of oxidized low density lipoproteins (Ox-LDL) with macrophages, endothelial and smooth muscle cells were thought to be major contributors to atherogenesis. However, there is growing evidence that extravasated erythrocytes along with iron and fibrin are also present in the atherosclerotic plaques, but the exact role of RBCs on atherosclerotic plaque formation is not known, demonstrating a significant gap in our knowledge. Furthermore, several studies have clearly shown that structure and function of RBCs are altered in atherosclerosis induced by environmental pollutants. Our long-term goal is to identify a process for preventive and therapeutic intervention of environmentally related cardiovascular diseases. The objective of this proposal is to elucidate how RBCs directly or indirectly play a major role in modifying LDL and its interaction with endothelial cells, which are the initial and crucial events in developing atherosclerosis. The central hypothesis is that modification of erythrocytes by environmental factors plays a significant role in the interaction between oxidized LDL and endothelial cells thereby leading to atherosclerosis. The rationale that underlies the proposed research is that, once we understand the role of RBCs in toxicant-induced atherosclerosis, this project may lead to new strategies that can be used to prevent and / or treat environmental / occupational related diseases. We will test our hypothesis by achieving the following two specific aims: (I) To determine the role of chemically modified RBCs in the oxidation of LDL and endothelial dysfunction leading to atherosclerosis (in vitro study). We will study this specific aim by pursuing two objectives. (la) Relationship between modified RBCs and Oxidized LDL: We will determine whether or not RBCs directly or indirectly modulate the oxidation of LDL Furthermore, we will determine if there are any structural and/or functional modifications within RBCs, following exposure to CS2. These experiments will provide information about whether there is a common link between modification of RBCs and oxidation of LDL, and whether or not this link is involved in the peroxide scavengers status of RBCs. (Ib) Role of chemically modified RBCs on endothelial dysfunction: We will determine whether RBCs directly or indirectly cause endothelial dysfunction by modulating (i) cell structure, (ii) the oxygen defense system, (iii) endothelial nitric oxide release and (iv) beta-adrenergic receptor coupling mechanisms. The results from these studies will provide a comprehensive understanding of the critical role of RBCs in the development of atherosclerosis. (II)To validate the in vitro result, an in vivo mouse model will be used to study whether modification of RBCs by an environmental toxicant (CS2) causes oxidation of LDL and endothelial cells dysfunction. We will determine the in vivo effect of CS2 on RBCs, LDL and endothelial cells by a single intratracheal injection into mice. This will not only validate the results found in vitro but also determine whether it is applicable to atherogenesis. Our expectation is that the results from this study will provide us with comprehensive understanding of the critical role of RBC's in environmental induced atherosclerosis. Furthermore, it will demonstrate the interaction between RBCs, LDL and endothelial cells. This study will be highly significant by increasing our knowledge of the mechanism(s) involved in atherogenesis induced by environmental pollutants.